Indexed by:期刊论文

Date of Publication:2018-07-14

Journal:Dalton transactions (Cambridge, England : 2003)

Included Journals:SCIE

Volume:47

Issue:26

Page Number:8619-8628

ISSN No.:1477-9234

Abstract:Os(ii) complexes are particularly interesting for triplet-triplet annihilation (TTA) upconversion, due to the strong direct S0  T1 photoexcitation, as in this way, energy loss is minimized and large anti-Stokes shift can be achieved for TTA upconversion. However, Os(bpy)3 has an intrinsic short T1 state lifetime (56 ns), which is detrimental for the intermolecular triplet-triplet energy transfer (TTET), one of the crucial steps in TTA upconversion. In order to prolong the triplet state lifetime, we prepared an Os(ii) tris(bpy) complex with a Bodipy moiety attached, so that an extended T1 state lifetime is achieved by excited state electronic configuration mixing or triplet state equilibrium between the coordination center-localized state (3MLCT state) and Bodipy ligand-localized state (3IL state). With steady-state and time-resolved transient absorption/emission spectroscopy, we proved that the 3MLCT is slightly above the 3IL state (by 0.05 eV), and the triplet state lifetime was prolonged by 31-fold (from 56 ns to 1.73 mus). The TTA upconversion quantum yield was increased by 4-fold as compared to that of the unsubstituted Os(ii) complex.